Various types of winding machines are known for the production of wound rolls from paper or cardboard webs longitudinally sectioned into individual webs.
In the so-called winding machines with carrying rollers, two driven carrying rollers form a roller bed in which the winding rolls lie in rows with aligned axes on the carrying rollers, which therefore bear the total weight of the winding rolls (DE 43 34 029-A). The winding hardness which is decisive for roll quality (=surface pressure between the layers of a winding roll) is clearly dependent on the tensile stress exerted during winding of the outermost layer. During winding, this tensile stress is produced by the driven carrying rollers and is decisively influenced by the line load and the geometric conditions in the nip between a winding roll and a carrying roller, since in the nip an additional stretching of the web is generated. The line load is the contact pressure of the winding rolls which is standard for a certain winding roll width, expressed in N/m. Since the stretching in the nip increases with the increasing roll weight, its value limits the maximal final diameter of a finished roll which is free of defects and wound with the desired winding hardness.
In order to be able to keep the line load within a desired low range, in winding machines with support rollers, on both sides of a central support roller, winding stations consisting each of two carrying elements are arranged, to which the individual webs are alternately fed for winding. Each winding station holds a winding roll by means of guide heads rotatably supported on the carrying elements, the heads being laterally introduced into the winding rolls. Thereby the guide heads bear all or part of the weight of the winding rolls. The balance of the winding roll weight--which can tend towards zero--is supported by the support roller. Such winding machines with support rollers make possible the winding of rolls with a large diameter and/or of very sensitive papers with the desired quality (DE 40 12 979-A1).
The support roller in winding machines with support rollers and one of the carrying rollers in the winding machines with carrying rollers serve at the same time as a contact rollers, which together with the winding roll form a roller nip through which the web is fed to the winding roll. A contact roller will have at the same time the function of preventing air from being sucked into the winding rolls, i.e. to seal off the winding rolls over their entire width.
In winding machines with carrying rollers, the tensile stress in the web required for the winding hardness is produced by the carrying rollers acting as a peripheral drive. The carrying rollers than can be connected with a rotary drive. In the winding machines with support rollers, the driven support rollers also act as a peripheral drive. In order to be able to additionally influence the winding hardness, particularly within the range of small winding roll diameters, it is known to provide the guide heads with rotary drives. By means of the rotary drives of the guide heads working as central or core drives it is possible to generate additional torque for influencing the tensile stress at each winding roll.
From the WO 97/28075 a winding machine with carrying rollers is known with two permanently driven carrying rollers. One of the carrying rollers has a shell made of a deformable layer consisting of a cellular plastic material with a plurality of evenly distributed pores and wit a compression modulus .kappa. of less than 10 MPa. The shell layer made of a volume-compressible material reduces the nip-induced stretching of the outermost layer of the winding roll in the roller nip to the carrying roller. In this way the winding of rolls with a larger final diameter is made possible, without damaging the paper or cardboard web and without the occurrence of winding defects in the wound rolls.
From WO 93/15007 it appears that in the case of larger winding rolls (roll widths exceeding 2 m, roll diameter more than 1000 mm), tears and creases can occur in the area of the roll core, if the roll weight borne by the guide head is too large. Therefore in a winding machine with support rollers it is proposed to additionally support the winding rolls below their center of gravity by means of an overpressure generated by compressed air, at a roll diameter of at least 1000 mm.
The WO 95/32908 describes a winding machine with support rollers wherein at the start of the winding process against the winding rolls pressure is exerted from above by rollers, which are swung downwards and from this point on support the winding rolls from underneath. Either roller pairs around which belts are revolving or which have a special soft coating are used.
In all known winding machines, the elements which are not primarily involved in the production of the desired winding hardness, such as elements for holding the winding rolls, for the support of the roll weight, for avoiding winding defects, etc., have at the same time a considerable influence on the winding hardness which is decisive in determining the quality of the wound rolls, or they are constructively very expensive.